Trickle: A Self-Regulating Algorithm for
Code Propagation and Maintenance in
Wireless Sensor Networks
Paper by David Culler, Philip Levis, Neil Patel, and Scott
Shenker
Presented by: Lee Hathcock
The Problem
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Code propagation in WSNs is costly
Desire an algorithm for scheduling code
propagation
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Low maintenance
Rapid propagation
Scalable
The solution? Trickle, of course.
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Few packets per hour, propagates in tens of
seconds, scales well, robust, and only 11 bytes
of state info
Trickle Overview
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Every once in a while, a node transmits code
“metadata” that represents its current code,
provided it hasn’t heard the same data recently.
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Either all nodes are up to date, or…
…a node needs to be updated.
If a node needs to be updated, it happens by
either…
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…a node hearing that it is out of date, and broadcasts its
metadata so it can be updated, or…
…a node hears that another node is out of date, and
sends an update to the code.
Trickle Algorithm
• “Polite gossip”
• Parameters
– c: a counter, incremented
each time a node hears its
own metadata
– k: a threshold, usually
between 1 and 2
– t: a timer value, between
the range of 0-
– : a time constant
Algorithm Analysis
• k*m packet
transmissions, but only
under the following
assumptions
– No packet loss
– Perfect interval
synchronization
– Single hop network
• Relax each of these
constraints
Algorithm Analysis
Conclusions
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Related work
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SPIN, SPIN-RL
SRM
Demers et al.
PlanetP
Reijers et al.
Assumes nodes always on
More of a scheduler than anything
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As such, can be used for more than code
propagation
References

P. Levis, N. Patel, D. Culler, and S. Shenker,
"Trickle: A self-regulating algorithm for code
propagation and maintenance in wireless
sensor networks," NSDI, 2004.